Avalanche forecast

Central Sierra Nevada

Sierra Avalanche Center
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Avalanche danger

Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Highlights

Human triggered wind slab avalanches may remain possible today due to wind slabs lingering in near and above treeline terrain. MODERATE avalanche danger exists on near and above treeline slopes. LOW avalanche danger exists in below treeline areas. Evaluate snow and terrain carefully before committing to a route. Use this information to identify features of concern like wind slabs and plan a route to avoid those areas of concern.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    Some wind slabs exist on near and above treeline slopes loaded by the east winds steeper than 35 degrees. These stiff wind slabs would be difficult to trigger, but it may still be possible for a skier to trigger one of these wind slabs today especially in complex or extreme terrain. Larger triggers like multiple people on a slope or large cornice collapses would have better chances of triggering one of these wind slabs. The largest of these wind slabs will exist on directly wind loaded NW-W-SW aspects, but they could also linger on some cross loaded N and S aspects as well.

    Blowing snow, cornices, wind scoured surfaces, ripples, and other wind created textures can help identify where wind slabs may exist. The hard wind slabs that exist on some aspects may also sound hollow due to the soft snow underneath them. 

Avalanche Discussion

Yesterday observations in the Donner Summit area showed firm wind slabs formed by the east winds on NW-W-SW aspects near ridgelines. Ski kicks on some test slopes where these wind slabs existed triggered some cracking and collapsing. Some of the wind loaded test slopes required several kicks or two people kicking the slope to trigger cracks in the firm and stubborn wind slabs. On Andesite Peak some natural cracking that looked to have occurred early yesterday morning also existed. Snowpit observations showed a firm, dense wind slab up to 18 inches thick resting on top of light, soft snow. Tests showed that if the wind slab did break the fracture could travel along the interface between the dense wind slab and the soft cold snow below it. East winds continued to transport snow throughout the day in this area. Across the Lake on Tamarack Peak, smaller wind slabs that did not extend very far away from ridgelines existed and cracking in these slabs was much more isolated and did not propagate very far. South of the Lake on Monument Peak, observers also reported less wind slab formation. In all of these areas: Donner Summit, Tamarack Peak, and Monument Peak, wind scoured surfaces existed on exposed near and above treeline N-NE-E-SE aspects with softer snow on the sheltered below treeline slopes. Sun crusts and sun affected snow started to exist on sun exposed slopes. 

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